The present invention relates to a stainless steel optimal to a corrosion- and wear-resistant die or the like used in a super-mirror-finished formation of resin parts and glass parts (particularly, such as optical disks and optical lenses) required to have an extremely high surface accuracy, which stainless steel, having excellent corrosion resistance property, is improved in the mirror-finished surface property, and to a method of producing the same.
Dies formed from a stainless steel of JIS SUS420J2 or the like by machining or grinding have been used in the fields of forming optical disks (e.g. CDs or DVD media) made of resin, optical lenses made of resin or glass, or the other optical parts (e.g. liquid crystal light-guide plates) made of resin. In the case of optical parts and so on made of resin, which are required to have an extremely high accuracy, a steel corresponding to the above mentioned JIS SUS420J2 have been sometime subjected to plating of amorphous Ni—P followed by machining with utilization of a diamond cutting tool to finish a forming surface in some cases after the amorphous plating thereof. Sometime a Cu alloy with a small amount of impurities has been likewise finished by machining.
On the other hand, there have been known a JIS SKD11 system steel and a JIS SUS440C system steel according to which the both properties of high corrosion resistance and high hardness can be compatibly realized. Further, there has been proposed, for example, a precipitation hardening stainless steel containing not more than 0.08 mass % (herein after merely referred to as “%”) of carbon, 2.0 to 5.0% of Si and 6.0 to 10.0% of Cr has been proposed. According to JP-A-2001-107194 (herein after referred to as Patent Document 1), the precipitation hardening stainless steel is further improved to attain a higher hardness by adding an appropriate amount of one or more of Mn, Ni, Mo, Cu, Nb, Ta, Ti and Co.